Synthesis And Characterization Of Core/shell Quantum Dots

In the field of fluorescent materials, quantum dots are playing a key role. Because of the limitation of core quantum dots in optical and electrical properties, core/shell quantum dots have attracted a great deal of attention. This work focuses on designing different shell structure to obtain core/shell quantum dots with outstanding optical properties. The synthesis is based on single-source precursor decomposition method which is convenient and low-costing.Through both single-source precursor and two precursors method, researchers have studied syntheses of zinc blend CdSe/CdS quantum dots with different shell layers. This work will discuss the influence of acid and metallic salt in synthesis of CdSe/CdS quantum dots. The dots after optimization show mono-disperse size distribution as well as great optical properties with excellent reproducibility.We further explores synthesis of CdSe/CdS/ZnS quantum dots by adding extra layers of ZnS shell. Because of the quasi-type-II band offsets of CdSe/CdS core/shell quantum dots, CdS shell alone is difficult to confine the photo-generated electrons and holes in a dot. As a result, CdSe/CdS quantum dots are relatively sensitive to the surface, and the layers of shell should be above15to obtain a good optical property. Because ZnS has a much wide bandgap, it can provide excellent confinement for both electrons and holes. With the extra layer(s) of ZnS, the quantum dots have a great improvement in optical properties. They show an obvious advantage at the high light power condition compared with the normal CdSe/CdS core/shell quantum dots.Besides the CdSe/CdS core/shell and CdSe/CdS/ZnS core/shell/shell quantum dots, CdSe/ZnCdS core/shell quantum dots with alloy shell have also been explored. The alloy-shelled quantum dots can remain nearly all advantages of CdSe/CdS quantum dots and provide unique characteristics in optical, heat, and surface sensitivity properties. Adjustment of composition of the alloy shell provides an extra tool for control of emission properties of quantum dots and brings in versatile options for various applications.